1. Field of the Invention
The present invention relates to a diagnostic agent for diabetes. More specifically, the present invention relates to a diagnostic agent for diabetes which comprises a compound labelled with 13C at least at one specific position.
2. Description of the Prior Art
Test methods generally used in the primary screening in diagnosis of diabetes are urine sugar test and fasting blood sugar level test. These tests are simple and high in specificity, but are low in sensitivity and give negative results for patients with light diabetes. Thus, 70% or more patients are missed and these tests are considered inadequate as screening tests for diabetes (Sekikawa et al., Medical Practice 10:63, 1933). On the other hand, the glucose tolerance test used for diagnosis of diabetes causes side effects due to administration of a large amount of glucose, and this test requires restraint of a subject for several hours and repeated collection of blood, imposing a heavy physical burden on the subject. Further, the procedures of this test are troublesome. Therefore, this test is actually impossible to carry out as a screening test for diabetes. Recently, blood HbA1C and fructosamine tests, which reflect the average blood sugar level of a subject for a certain period in the past, have been introduced as screening tests for diabetes in some facilities. Under the existing circumstances, however, even these tests cannot be said to be adequate in sensitivity and specificity for light diabetes, and there remains the problem of difference in measurement results among facilities.
Blood sugar level, HbA1C and fructosamine tests have been used widely for management of outpatients with diabetes and evaluation of therapeutic effects. However, since blood sugar levels will drop at the time of fasting in the case of light diabetes, they cannot be a criterion for the evaluation. HbA1C and fructosamine tests have, in addition to the above-described problems, the following problem: the results of these tests cannot be known until the next visit to the hospital, so instructions are given to the patient on the basis of the past test results.
Under such circumstances, there is a demand for development of a test method for diagnosis of diabetes, management of patients with diabetes and evaluation of therapeutic effects, which method is effective even for patients with light diabetes, does not impose a heavy burden on subjects, and gives results immediately and accurately.
It is an object of the present invention to provide a diagnostic agent for diabetes which is effective even for patients with light diabetes, does not impose a heavy burden on subjects, and can give accurate test results immediately.
As a result of their eager researches toward the solution of the above problems, the present inventors have found that it is possible to diagnose diabetes accurately by administering to a subject a compound labelled with 13C at least at one specific position and measuring the degree of increase of 13C levels in the exhaled CO2. Thus, the present invention has been achieved.
The present invention relates to a diagnostic agent for diabetes, comprising a compound labelled with 13C at least at one specific position selected from the group consisting of the following (a) to (g):
(a) galactose, fructose or xylose labelled with 13C at least at one specific position, or a starch composed of glucose units labelled with 13C at least at one specific position;
(b) an amino acid labelled with 13C at least at one specific position;
(c) lactic acid or citric acid labelled with 13C at least at one specific position;
(d) a fatty acid labelled with 13C at least at one specific position;
(e) a glyceride labelled with 13C at least at one specific position;
(f) glycerol labelled with 13C at least at one specific position; and
(g) aminopyrin of which the dimethylamino group at position 4 is labelled with 13C, phenacetin of which the ethoxy group is labelled with 13C at position 1, or methacetin of which the methoxy group is labelled with 13C.